Isotropic dispersion function for the northeast spiral arm as a function of ℓ ² (top) and ℓ (middle). The broken curve ("ordered") is the least-squares fit for the sum of the turbulent-to-total magnetic energy ratio and the ordered component to data contained within 6 ⩽ ℓ ⩽ 10; data are represented with symbols. Bottom: the magnetized turbulence autocorrelation function b ²(ℓ) obtained by subtracting the data from the aforementioned fit of the middle graph. The broken curve shows the radial profile of the "mean autocorrelated synthesized beam."